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Design of Organic Semiconductors: Tuning the Electronic Properties of π‐Conjugated Oligothiophenes with the 3,4‐Ethylenedioxythiophene (EDOT) Building Block
Author(s) -
Turbiez Mathieu,
Frère Pierre,
Allain Magali,
Videlot Christine,
Ackermann Jörg,
Roncali Jean
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200401058
Subject(s) - conjugated system , thiophene , intramolecular force , materials science , cyclic voltammetry , homo/lumo , organic field effect transistor , crystallography , photochemistry , polymer chemistry , electrochemistry , polymer , chemistry , molecule , organic chemistry , field effect transistor , electrode , transistor , physics , quantum mechanics , composite material , voltage
Hybrid oligothiophenes based on a various combinations of thiophene and 3,4‐ethylenedioxythiophene (EDOT) groups have been synthesized. UV/Vis absorption spectra show that the number and relative positions of the EDOT groups considerably affect the width of the HOMO–LUMO gap and the rigidity of the conjugated system. Analysis of the crystallographic structure of two hybrid quaterthiophenes confirms that insertion of two adjacent EDOT units in the middle of the molecule leads to a self‐rigidification of the conjugated systems by intramolecular S⋅⋅⋅O interactions. Cyclic voltammetry data shows that the first oxidation potential of the oligomers decreases with increasing chain length and increasing number of EDOT groups for a given chain length. Electrochemical studies and theoretical calculations show that the positions of the EDOT units in the conjugated chain control the potential difference (Δ E p ) between the first and second oxidation steps. Moving the EDOT groups from the outer to the inner positions of the conjugated system increases Δ E p . Theoretical calculations confirm that this phenomenon reflects an increase of the intramolecular coulombic repulsion between positive charges in the dication. A thin‐film field‐effect transistor was fabricated by vacuum sublimation of a pentamer with alternating thiophene–EDOT structure, and the hole mobility was determined.